1. Field of the Invention
The present invention relates to a liquid-jet head and a liquid-jet apparatus. More specifically, the present invention relates to ink-jet recording head configured such that an vibration plate partially constitutes a pressure generation chamber communicating with a nozzle orifice, through which a droplet of ink is ejected, and such that a piezoelectric element is provided via the vibration plate so as to eject a droplet of ink through displacing movement thereof, as well as to an ink-jet recording apparatus using the head.
2. Description of the Related Art
An ink-jet recording head is configured such that a vibration plate partially constitutes a pressure generation chamber communicating with a nozzle orifice, through which a droplet of ink is ejected, and such that a piezoelectric element causes the vibration plate to be deformed, thereby pressurizing ink contained in the pressure generation chamber and thus ejecting a droplet of ink through the nozzle orifice. Ink-jet recording heads which are put into practical use are classified into the following two types: an ink-jet recording head that employs a piezoelectric actuator operating in longitudinal vibration mode; i.e., expanding and contracting in the axial direction of a piezoelectric element; and an ink-jet recording head that employs a piezoelectric actuator operating in flexural vibration mode.
The former recording head has an advantage in that a function for changing the volume of a pressure generation chamber can be implemented through an end face of a piezoelectric element abutting a vibration plate, thereby exhibiting good suitability to high-density printing. However, the former recording head has a drawback in that a fabrication process is complicated; specifically, fabrication involves a difficult process of dividing the piezoelectric element into comb-tooth-like segments at intervals corresponding to those at which nozzle orifices are arranged, as well as a process of fixing the piezoelectric segments in such a manner as to be aligned with corresponding pressure generation chambers.
The latter recording head has an advantage in that piezoelectric elements can be formed on a vibration plate through a relatively simple process; specifically, a green sheet of piezoelectric material is overlaid on the vibration plate in such a manner as to correspond in shape and position to a pressure generation chamber, followed by firing. However, the latter recording head has a drawback in that a piezoelectric element must assume a certain amount of area in order to utilize flexural vibration, thus involving difficulty in arranging pressure generation chambers in high density.
In order to solve the drawback of the latter recording head, as disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 1993-286131, the following process has been proposed. An even layer of piezoelectric material is formed on the entire surface of a vibration plate by use of a film deposition technique. By means of lithography the layer of piezoelectric material is divided in such a manner as to correspond in shape and position to pressure generation chambers, thereby forming independent piezoelectric elements corresponding to the pressure generation chambers.
In such an ink-jet recording head, ink supply paths are formed in a passage-forming substrate, in which pressure generation chambers are formed, such that each ink supply path communicates with a longitudinal end portion of the corresponding pressure generation chamber and is shallower than the pressure generation chamber. The ink supply paths regulate the flow resistance of ink flowing therethrough so as to supply ink to the individual pressure generation chambers at a constant flow rate.
Such ink supply paths are commonly formed by half-etching the passage-forming substrate. However, the depth of half-etching is difficult to control; as a result, the depth of ink supply paths varies among ink-jet recording heads. Since the flow resistance of ink flowing through individual ink supply paths varies among ink-jet recording heads, ink ejection characteristics are not stabilized among the ink-jet recording heads.
Note that the foregoing problems are not limited to ink-jet recording heads for ejecting ink, but are also applicable naturally to other liquid-jet heads for ejecting liquids other than ink.